1. Field of the Invention
The present invention relates to a detector for detecting a physical quantity from a value of an electric signal converted from the physical quantity, and, more particularly, to a detector having a self-calibration function and a characteristic corrective function.
2. Related Art Statement
Hitherto, a conventional detector has been, as disclosed in, for example, Japanese Patent Unexamined Publication No. 61-31952, arranged in such a manner that the measuring operation is stopped so as to start a calibrating operation which is performed as the offline work. Furthermore, there has been disclosed, in Japanese Patent Unexamination Publication No. 61-212753, an apparatus capable of diagnosing deterioration by analyzing the characteristics observed in the detector. However, the apparatus of this type also performs, as the offline work, the operation for diagnosing the deterioration.
The conventional calibration has been realized for the purpose of automating the offline work. Furthermore, there has been a proposal that the reliability of a detector is improved by observing the line and giving an alarm if necessary as the online work. However, since no measure has been taken for performing the calibration as the online work, a problem takes place that the measurement is stopped for a relatively long time in comparison with the time in which the value of the measurement can be changed.